U.S. patent number 6,907,243 [Application Number 09/591,077] was granted by the patent office on 2005-06-14 for method and system for dynamic soft handoff resource allocation in a wireless network.
This patent grant is currently assigned to Cisco Technology, Inc.. Invention is credited to Achal R. Patel.
United States Patent |
6,907,243 |
Patel |
June 14, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
Method and system for dynamic soft handoff resource allocation in a
wireless network
Abstract
A method and system for dynamic soft handoff resource allocation
in a wireless communications network includes determining a
wireless path characteristic individually for each path of a macro
diversity connection between a mobile device and a plurality of
wireless sites. Wireless resources are allocated for the macro
diversity connection between the mobile device and the wireless
sites based on the wireless path characteristic. The wireless path
characteristic includes a location-based characteristic, a
congestion-based characteristic, a subscriber-based characteristic
and/or a performance-based characteristic.
Inventors: |
Patel; Achal R. (McKinney,
TX) |
Assignee: |
Cisco Technology, Inc. (San
Jose, CA)
|
Family
ID: |
34635980 |
Appl.
No.: |
09/591,077 |
Filed: |
June 9, 2000 |
Current U.S.
Class: |
455/442; 370/329;
370/335; 455/436; 455/450; 455/509; 455/453; 455/440; 370/331 |
Current CPC
Class: |
H04W
72/044 (20130101); H04W 52/143 (20130101); H04W
52/242 (20130101); H04W 52/247 (20130101); H04W
52/40 (20130101); H04W 52/343 (20130101); H04W
4/24 (20130101); Y02D 70/164 (20180101); H04W
36/18 (20130101); H04W 40/02 (20130101); Y02D
30/70 (20200801); H04B 17/309 (20150115); Y02D
70/30 (20180101); Y02D 70/142 (20180101) |
Current International
Class: |
H04Q
7/00 (20060101); H04B 7/00 (20060101); H04B
7/204 (20060101); H04Q 7/20 (20060101); H04B
7/216 (20060101); H04Q 007/20 (); H04Q 007/00 ();
H04B 007/00 (); H04B 007/216 () |
Field of
Search: |
;455/438,440,442,450,436,437,63,67.1,101 ;370/329,331,335 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
0 831 669 |
|
Mar 1998 |
|
EP |
|
0 831 669 |
|
Mar 1998 |
|
EP |
|
1 041 850 |
|
Oct 2000 |
|
EP |
|
WO 99/53630 |
|
Oct 1999 |
|
WO |
|
Other References
International Search Report in International Application No. PCT/US
00/16210, dated Oct. 19, 2000, 7 page..
|
Primary Examiner: Chin; Vivian
Assistant Examiner: Persino; Raymond B.
Attorney, Agent or Firm: Baker Botts L.L.P.
Parent Case Text
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent
Application Serial No. 60/138,224 entitled "Method and Apparatus
for Quality of Service (QoS) and Air Congestion Based Resource
Allocation for Packet Delivery Wireless Networks" filed Jun. 9,
1999, and which is hereby incorporated by inference.
Claims
What is claimed is:
1. A method for allocating resources in a wireless network for
macro diversity connections, comprising: determining a wireless
path characteristic individually for each path of a macro diversity
connection between a mobile device and a plurality of wireless
sites, the wireless path characteristic comprising a location-based
characteristic, the location-based characteristic for a path
determined by determining traffic loading for the wireless sites in
a region of the mobile device; allocating wireless resources for
the macro diversity connection between the mobile device and the
wireless sites based on the wireless path characteristic; and
individually allocating wireless resources between the mobile
device and each wireless site based on the wireless path
characteristic for the wireless site.
2. The method of claim 1, further comprising allocating wireless
resources at each wireless site based on the wireless path
characteristics for the wireless site.
3. The method of claim 1, wherein the wireless resources comprise
site transmission resources.
4. The method of claim 3, wherein the transmission resources
comprise transmission bandwidth.
5. The method of claim 3, wherein the transmission resources
comprise transmission power.
6. The method of claim 3, further comprising: receiving a requested
level for a transmission resource from the mobile device;
determining a bias for each wireless site based on the wireless
path characteristic for the wireless site; determining an
allocation level for the transmission resource at each wireless
site based on the requested level and the bias for the wireless
site; and allocating the allocation level for the transmission
resource at each wireless site.
7. The method of claim 6, wherein the transmission resource
comprises transmission power.
8. The method of claim 6, wherein the transmission resource
comprises transmission bandwidth.
9. The method of claim 1, wherein the wireless site comprises a
wireless server.
10. The method of claim 1, wherein the wireless site comprises a
cell site for a terrestrial wireless communication system.
11. The method of claim 10, wherein the cell site comprises a base
station.
12. The method of claim 1, further comprising dynamically
reallocating wireless resources between the mobile device and the
wireless sites.
13. The method of claim 1, further comprising: determining an
updated set of the wireless path characteristics during a duration
of the macro diversity connection; and reallocating the wireless
resources based on the updated wireless path characteristics.
14. The method of claim 1, further comprising: repeatedly
determining an updated set of wireless path characteristics during
the macro diversity connection; and reallocating the wireless
resources based on the updated wireless path characteristics.
15. The method of claim 1, wherein the macro diversity connection
is a soft handoff connection.
16. The method of claim 15, wherein the soft handoff connection is
a code-division multiple access (CDMA) connection.
17. The method of claim 16, wherein the CDMA connection is a CDMA
2000 connection.
18. The method of claim 16, wherein the CDMA connection is a W-CDMA
connection.
19. The method of claim 1, wherein the mobile device is a cellular
telephone.
20. The method of claim 1, wherein the mobile device is a portable
Internet device.
21. The method of claim 1, further comprising receiving the
identity of the wireless sites from the mobile device.
22. The method of claim 1, determining the location-based
characteristic for a path comprising determining a radio frequency
(RF) path loss for the path.
23. The method of claim 1, determining the location-based
characteristic for a path comprising determining a maximum
allowable path loss (MAPL) for the path.
24. The method of claim 1, determining the location-based
characteristic for a path comprising determining a distribution of
active users in wireless sites in a region of the wireless
device.
25. The method of claim 1, further comprising allocating no
resources between the mobile device and a wireless site having a
low performing path.
26. The method of claim 25, wherein the low performing path
provides negligible contribution to the macro diversity
connection.
27. The method of claim 1, wherein the wireless path characteristic
comprises a congestion-based characteristic.
28. The method of claim 27, determining the congestion-based
characteristic for a path comprising determining available
transmission resources at a corresponding wireless site.
29. The method of claim 28, wherein the transmission resources
comprise transmission power.
30. The method of claim 28, wherein the transmission resources
comprise transmission bandwidth.
31. The method of claim 1, wherein the wireless path characteristic
comprises a subscriber-based characteristic.
32. The method of claim 31, wherein the subscriber-based
characteristic comprises a quality of service (QoS)
characteristic.
33. The method of claim 32, further comprising allocating wireless
resources proportionally to QoS.
34. The method of claim 32, further comprising allocating wireless
resources from only a single wireless site for best effort QoS
traffic.
35. The method of claim 32, further comprising allocating all
wireless resources requested by a mobile device for premium QoS
traffic.
36. The method of claim 31, further comprising allocating a subset
of wireless resources requested by a mobile device for best effort
traffic when sufficient wireless resources are not available for
all requested wireless resources.
37. The method of claim 1, wherein the wireless path characteristic
comprises a performance-based characteristic.
38. The method of claim 37, determining the performance-based
characteristic for a path comprising collecting real-time
performance parameters for the path.
39. The method of claim 38, wherein the real-time performance
parameters comprise packet error rates.
40. The method of claim 38, wherein the real-time performance
parameters comprise real-time delays.
41. The method of claim 38, wherein the real-time performance
parameters comprise packet retransmissions.
42. The method of claim 37, determining the performance-based
characteristic comprising determining resource redundancy of a
previous resource allocation.
43. The method of claim 37, wherein the allocated wireless
resources between the mobile device and the wireless sites
substantially comprise minimum resources operable to maintain the
macro diversity connection in accordance with a subscribed
service.
44. The method of claim 1, wherein the wireless path characteristic
comprises at least two of a location-based characteristic, a
congestion-based characteristic, a subscriber-based characteristic,
and a performance-based characteristics.
45. The method of claim 1, wherein the wireless path characteristic
comprises at least three of a location-based characteristic, a
congestion-based characteristic, a subscriber-based characteristic,
and a performance-based characteristic.
46. The system of claim 1, the logic further operable to determine
the location-based characteristic for a path by determining a radio
frequency (RF) path loss for the path.
47. The system of claim 1, the logic further operable to determine
the location-based characteristic for a path by determining a
maximum allowable path loss (MAPL) for the path.
48. The system of claim 1, the logic further operable to determine
the location-based characteristic for a path by determining a
distribution of active users in wireless sites in a region of the
wireless device.
49. The system of claim 1, the logic further operable to allocate
no resources between the mobile device and the wireless site having
a low performing path.
50. The system of claim 49, wherein the low performing path
provides negligible contribution to the macro diversity
connection.
51. A method for allocating resources in a wireless network for
macro diversity connections, comprising: determining a wireless
path characteristic individually for each path of a macro diversity
connection between a mobile device and a plurality of wireless
sites, the wireless path characteristic comprising a location-based
characteristic, the location-based characteristic for a path
determined by determining traffic loading for the wireless sites in
a region of the mobile device; allocating wireless resources for
the macro diversity connection between the mobile device and the
wireless sites based on the wireless path characteristic; and
allocating the wireless resources by allocating a requested
bandwidth to a subset of the wireless sites.
52. The method of claim 1, wherein the wireless resources allocated
between the mobile device and the wireless sites substantially
comprise minimum resources to maintain the macro diversity
connection between the mobile device and a network including the
wireless sites.
53. A system for allocating resources in a wireless network for
macro diversity connections, comprising: logic stored in
computer-processable media; and the logic operable to: determine a
wireless path characteristic individually for each path of a macro
diversity connection between a mobile device and a plurality of
wireless sites, the wireless path characteristic comprising a
location-based characteristic, the location-based characteristic
for a path determined by determining traffic loading for the
wireless sites in a region of the mobile device; allocate wireless
resources for the macro diversity connection between the mobile
device and the wireless sites based on the wireless path
characteristic; and individually allocate wireless resources
between the mobile device and each wireless site based on the
wireless path characteristic for the wireless site.
54. The system of claim 53, further comprising allocating wireless
resources at each wireless site based on the wireless path
characteristic for the wireless site.
55. The system of claim 53, wherein the wireless resources comprise
transmission resources.
56. The system of claim 55, wherein the transmission resources
comprise transmission bandwidth.
57. The system of claim 55, wherein the transmission resources
comprise transmission power.
58. The system of claim 55, the logic further operable to receive a
requested level for a transmission resource from the mobile device,
determine a bias for each wireless site based on the wireless path
characteristic for the wireless site, determine an allocation level
for the transmission resource at each wireless site based on the
requested level and the bias for the site, and allocate the
allocation level for the transmission resource at each wireless
site.
59. The system of claim 58, wherein the transmission resource
comprises transmission power.
60. The system of claim 58, wherein the transmission resource
comprises transmission bandwidth.
61. The system of claim 53, wherein the wireless site comprises a
wireless server.
62. The system of claim 53, wherein the wireless site comprises a
cell site for a terrestrial wireless communication system.
63. The system of claim 62, wherein the cell site comprises a base
station.
64. The system of claim 53, the logic further operable to
dynamically reallocate wireless resources between the mobile device
and the wireless sites.
65. The system of claim 53, the logic further operable to determine
an updated set of wireless path characteristics during a duration
of a macro diversity connection and to reallocate the wireless
resources based on the updated wireless path characteristics.
66. The system of claim 53, the logic further operable to
repeatedly determine an updated set of wireless path
characteristics during the macro diversity connection and to
reallocate the wireless resources based on the updated wireless
path characteristics.
67. The system of claim 53, wherein the macro diversity connection
is a soft-hand-off connection.
68. The system of claim 67, wherein the soft-handoff connection is
a code-division multiple access (CDMA) connection.
69. The system of claim 68, wherein the CDMA connection is a CDMA
2000 connection.
70. The system of claim 68, wherein the CDMA connection is a WCDMA
connection.
71. The system of claim 53, wherein the mobile device is cellular
telephone.
72. The system of claim 53, wherein the mobile device is a portable
Internet device.
73. The system of claim 53, the logic further operable to receive
the identity of the wireless sites from the mobile device.
74. The system of claim 73, the logic further operable to allocate
the wireless resources by allocating a requested transmission
resource through a subset of the wireless sites.
75. The system of claim 53, wherein the wireless resources
allocated between the mobile device and the wireless sites
substantially comprise minimum resources to maintain the macro
diversity connection between the mobile device and a network
included in the wireless sites.
76. The system of claim 53, wherein the wireless path
characteristic comprises a congestion-based characteristic.
77. The system of claim 76, the logic further operable to determine
the congestion-based characteristic for a path by determining
available transmission resources at a corresponding wireless
site.
78. The system of claim 76, wherein the transmission resources
comprise transmission power.
79. The system of claim 77, wherein the transmission resources
comprise transmission bandwidth.
80. The system of claim 53, wherein the wireless path
characteristic comprises a subscriber-based characteristics.
81. The system of claim 80, wherein the subscriber-based
characteristic comprises a quality of service (QoS)
characteristic.
82. The system of claim 81, the logic further operable to allocate
wireless resources proportionally to QoS.
83. The system of claim 81, the logic further operable to allocate
wireless resources from only a single wireless site for best effort
QoS traffic.
84. The system of claim 81, the logic further operable to allocate
all wireless resources requested by a mobile device for premium QoS
traffic.
85. The system of claim 80, the logic further operable to allocate
a subset of wireless resources requested by mobile device for best
effort traffic when sufficient wireless resources are not available
for all requested wireless resources.
86. The system of claim 53, wherein the wireless path
characteristic comprises a performance-based characteristic.
87. The system of claim 86, the logic further operable to determine
the performance-based characteristic for a path by collecting
real-time performance for the path.
88. The system of claim 87, wherein the real-time performance
parameters comprise packet error rates.
89. The system of claim 87, wherein the real-time performance
parameters comprise real-time delays.
90. The system of claim 87, wherein the real-time performance
parameters comprise packet retransmissions.
91. The system of claim 86, the logic further operable to determine
the performance-based characteristic by determining resource
redundancy of a previous resource allocation.
92. The system of claim 86, wherein the allocated wireless
resources between the mobile device and the wireless sites
substantially comprise minimum resources operable to maintain the
macro diversity connection in accordance with a subscribed
service.
93. The system of claim 53, wherein the wireless path
characteristic comprise at least two of a location-based
characteristic, a congestion-based characteristic, a
subscriber-based characteristic, and a performance-based
characteristic.
94. The system of claim 53, wherein the wireless path
characteristic comprise at least three of a location-based
characteristic, a congestion-based characteristic, a
subscription-based characteristic, and a performance-based
characteristic.
95. A mobile gateway for a wireless network, comprising: a data
input subsystem operable to collect historical, real-time,
subscription and location information for wireless devices
communicating with the wireless network; a resource
characterization system operable to access data in the data input
system and to determine a wireless path characteristic individually
for each path of a macro diversity connection between a mobile
device and a plurality of wireless sites in the wireless network
based on the collected data; and a soft handoff controller operable
to allocate wireless resources for the macro diversity connection
between the mobile device and the wireless sites based on the
wireless path characteristic and to individually allocate wireless
resources between the mobile device and each wireless site based on
the wireless path characteristic for the wireless site.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to the field of wireless
communications, and more particularly to an improved method and
system for dynamic soft hand off resource allocation in a wireless
network.
BACKGROUND OF THE INVENTION
Wireline and wireless Internet Protocol (IP) networks have
traditionally supported a best effort delivery of all traffic.
However, current networks are optimized for real-time voice
services, despite the growing need for data services. Furthermore,
the constraints imposed by voice and data traffic on the system are
quite different. Voice transmissions must be in real time and are
intolerant to delays. Large delays in the transmission of voice
packets significantly reduce the quality of the voice link. Also,
network Grade of Service (GoS) requirements, such as probability of
call blocking or outage and area reliability, as well as the
treatment offered to all mobile voice users is the same. On the
other hand, many data applications are tolerant to reasonable
delays without significantly impacting the link and application
quality. Thus, quality of service requirements and the treatment
required by different data applications are dissimilar.
To support enhanced services, multiple types, or classes, of
services have been established and assigned certain quality of
service (QoS) parameters that manage queues for each service type.
The QoS parameters include delay, jitter, error rates, and
throughput. The QoS parameters can be provisioned on a per Internet
Protocol (IP) connection or per flow basis through mechanisms such
as resource reservation protocol (RSVP) or can be provisioned on
aggregate flow, which is classified into service classes. Internet
service providers (ISPs) can utilize the service classes, their
associated QoS behavior, and QoS provisioning to provide multiple
service offerings to their business and consumer customers.
As newer classes of services, with differing QoS requirements and
different transmission characteristics are offered, it becomes
imperative for wireless carriers to find new methods and techniques
to optimally utilize limited air-bandwidth without affecting the
overall network GoS. One attempt to ensure continual coverage, and
thereby maintain QoS, is the "soft handoff." In modern wireless
networks, Code-Division Multiple Access (CDMA) technology is used
to shares frequency across multiple users and applications. CDMA
supports a soft handoff, in which a mobile user is communicating
with a mobile switching center via two or more cellular antennae
sites and the user data is broadcast by all sites to the mobile
user. This mode of communication makes the mobile-to-cell link
resilient to obstructions in the beam path that can cause the
active call to terminate abruptly. For the mobile to drop a call,
the paths to all of the cells would have to be obstructed. A
greater number of active links between the mobile and the network
lowers the probability of dropping a call.
But, a mobile unit in soft handoff will cause all sites in handoff
to transmit over a forward link to the mobile unit. This forward
transmission from multiple sites to a single mobile unit, while
improving the communication link to that particular mobile unit,
increases the overall interference for other active mobile units in
the system and can potentially degrade the performance of the
forward link for all mobile units. Also, as the total forward power
is limited, the available power for new users is considerably
reduced. If several mobile units are in soft handoff at the same
time, this can potentially lead to severe degradation in the
overall system capacity.
SUMMARY OF THE INVENTION
The present invention provides an improved method and system for
dynamic soft handoff and other macro diversity resource allocation
in a wireless communications network that substantially eliminate
or reduce problems and disadvantages associated with previous
methods and systems. In particular, mobile users are characterized
based on their relative impact on the network to manage the forward
link interference caused by the mobile users in the soft
handoff.
In accordance with one embodiment of the present invention, a
method and system for allocating resources in a wireless network
for macro diversity connections includes determining individual
wireless path characteristics for each path of the macro diversity
connection between a mobile device and a plurality of wireless
sites. Wireless resources for the macro diversity connection are
allocated between the mobile device and the wireless sites based on
the wireless path characteristics.
The wireless path characteristics comprise location-based
characteristics, interference-based characteristics,
subscription-based characteristics and/or performance-based
characteristics. The location-based characteristics include the
location of the device along with related statistical information
that allow the minimum resources needed from each site to meet
subscriptions requirements to be determined. The interference-based
characteristics include available bandwidth that allows intelligent
allocation of resources to reduce air congestion and improved
system capacity. The subscription-based characteristics include
Quality of Service (QoS) that allow a fair distribution of resource
in which higher level subscribers are provided more resources than
lower level subscribers. The performance-based characteristics
include real-time performance parameters to minimize redundancy and
resource allocation.
Technical advantages of the present invention include providing an
improved method and system for dynamic soft handoff and other macro
diversity resource allocation in a wireless communications network.
In particular, the active sets of mobile units communicating over
wireless networks are biased to vary the resources allocated to a
particular mobile unit. The bias values may be determined based on
the geographic location (geo-location) of the mobile units, air
congestion on the network, QoS subscriptions, link performance
data, or any suitable combination of the above. This dynamic
resource allocation for data/IP packet delivery over an air
interface improves system capacity and allows for differentiated
service provisions among mobile users. Moreover, management of
system capacity among users and applications with differentiated
service requests is improved.
Another technical advantage of the present invention includes
providing an improved method and system for dynamic, location-based
soft handoff resource allocation in a wireless communications
network. In particular, the active sets of mobile units on the
network are biased according to the geo-location of the mobile
units relative to the location of neighboring servers. Thus, real
time RF performance parameters and geo-location measurements of a
mobile unit, along with historical data and adaptive capacity
estimation techniques are used to compute dynamic resource
allocation biases. Therefore, mobile unit servers that are not
adding tangible value to the quality of the communications may be
removed from communication with a mobile unit, thereby allowing
allocation of those resources to other mobile units.
Yet another technical advantage of the present invention includes
providing an improved method and system for dynamic,
congestion-based soft handoff resource allocation in a wireless
communications network. In particular, the active sets of mobile
units on the network are biased according to the available power of
the individual servers and the minimal requirements of each mobile
unit. As a result, the dynamic resource allocation biases minimize
air-link congestion in wireless multi-media networks.
Yet another technical advantage of the present invention includes
providing a method and system for dynamic, subscription-based soft
handoff resource allocation in a wireless communications network.
In particular, the active sets of mobile units on the network are
biased according to the level of quality subscription for each
mobile user. Multiple service types may be different quality of
service (QoS) classes such as premium, assured, and best effort.
Thus, dynamic allocation of resources allows use of QoS
subscriptions and requirements of mobile users and applications to
compute dynamic resource allocation biases and allocate resources
fairly. Furthermore, a user who has subscribed to a higher level of
service is provided with more resources than a user who has
subscribed to a lower level of service.
Still another technical advantage of the present invention includes
providing a method and system for dynamic, performance-based soft
handoff resource allocation in a wireless communications network.
In particular, the active sets of mobile units on the network are
biased according to the measured performance data of a current
wireless link. Thus, a network operator may maximize efficiency in
resources by estimating redundancy in resource allocation and
minimizing that redundancy.
Yet another technical advantage of the present invention includes
providing intelligent control for resource allocation. In
particular, the network operator can manage the forward link
interference caused by the plurality of mobile users in a soft
handoff configuration. The mobile users can be characterized based
on their relative impact on the network by considering the loading
in the neighboring sectors, QoS subscriptions and the geo-location
of all active mobile units in the neighboring sectors. Resource
allocation can be controlled by generating tiered active sets that
will minimize the interference and maintain the subscribed QoS for
all users. Thus, network operators are assisted in effectively
managing the air bandwidth, and thereby the congestion in heavily
loaded portions of the network while providing fair and equitable
quality of service to mobile users with varied QoS subscriptions
and requirements.
Other technical advantages of the present invention will be readily
apparent to one skilled in the art from the following figures,
description, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention and its
advantages, reference is now made to the following description
taken in conjunction with the accompanying drawings, wherein like
reference numerals represent like parts, in which:
FIG. 1 is a block diagram illustrating a wireless network in
accordance with one embodiment of the present invention;
FIG. 2 is a block diagram illustrating details of the mobile
gateway of FIG. 1 in accordance with one embodiment of the present
invention;
FIG. 3 is a graphical diagram illustrating soft handoff for a
mobile device in accordance with one embodiment of the present
invention;
FIG. 4 is a flow diagram illustrating a method for allocating
resources for a soft handoff connection in accordance with one
embodiment of the present invention;
FIG. 5 is a flow diagram illustrating a method for determining path
characteristics for a soft handoff connection in accordance with
one embodiment of the present invention;
FIG. 6 is a flow diagram illustrating a method for allocating
resources soft handoff connections using location-based
characteristics in accordance with one embodiment of the present
invention;
FIG. 7 is a graphical diagram illustrating a location-based soft
handoff system for the network of FIG. 1 in accordance with one
embodiment of the present invention;
FIG. 8 is a flow diagram illustrating a method for allocating
resources for soft handoff connections using congestion-based
characteristics in accordance with one embodiment of the present
invention;
FIG. 9 is a graphical diagram illustrating a congestion-based soft
handoff system for the network of FIG. 1 in accordance with one
embodiment of the present invention;
FIG. 10 is a flow diagram illustrating a method for allocating
resources for soft handoff connections using subscription-based
characteristics in accordance with one embodiment of the present
invention;
FIG. 11 is a graphical diagram illustrating a subscription-based
soft handoff system for the network of FIG. 1 in accordance with
one embodiment of the present invention;
FIG. 12 is a flow diagram illustrating a method for allocating
resources for soft handoff connections using performance-based
characteristics in accordance with one embodiment of the present
invention; and
FIG. 13 is a graphical diagram illustrating a performance-based
soft handoff system for the network of FIG. 1 in accordance with
one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a wireless network 10 in accordance with one
embodiment of the present invention. In this embodiment, the
wireless network 10 is a cellular network in which terrestrial
wireless transmission originates in geographically delimited cells.
It will be understood that the present invention may be used in
connection with satellite and other suitable wireless and other
dynamic bandwidth networks.
Referring to FIG. 1, the wireless network 10 covers a contiguous
area that is broken down into a series of overlapping wireless
sites such as cells 12. Each cell 12 has a base station, or server,
14 and may be subdivided into a plurality of geographic location
(geo-location) areas 16. The geo-location areas 16 are each a
defined area in which bandwidth may be allocated to mobile devices.
The geo-location areas 16 may have a resolution greater than, less
than, or equal to cell size. In a particular embodiment, the
geo-location areas 16 are substantially square in shape to form a
contiguous grid over the coverage area. Thus, the geo-locations 16
may be shared by one or more cells 12. Further information
regarding the geo-location is described in co-owned U.S. patent
application Ser. No. 09/466,308, titled Method and System for
Allocating Bandwidth in a Wireless Communications Network, filed
Dec. 17, 1999, and incorporated herein by reference.
Each server 14 provides a radio frequency (RF) link for mobile
devices 18 within its cell 12. The wireless RF link to the mobile
devices 18 in the cell 12 may be based on established standards
such as IS-54 (TDMA), IS-95 (CDMA), GMS and AMPS, 802.11 based
WLAN, or new upcoming standards such as CDMA 2000 and W-CDMA, or
proprietary radio interfaces. The mobile devices 18 may be cell
phones, data phones, data devices, portable computers, or any other
suitable device capable of communicating information over a
wireless link.
Due to the nature of the RF airlink, the interference generated by
the usage of various mobile devices 18 is inter-dependent. That is,
the interference generated by the usage of a mobile device 18
including transmitting and receiving signals is not only dependent
on its geo-location, but is also dependent on the geo-location of
surrounding mobile devices 18 and the usage of those devices. Thus,
the cellular network is an inherently interference-limited network
with bandwidth usage in a particular location impacting the
interference in specific areas of the neighborhood. In the complete
spectrum sharing systems such as CDMA and W-CDMA, bandwidth usage
in a particular area directly impacts the bandwidth available at
different locations in the neighborhood.
The servers 14 each have a defined bandwidth with which to
communicate with the mobile devices 18 in the cells 12. The
bandwidth is used by the server 14 and the mobile devices 18 to
communicate voice and data information. The supported bandwidth is
a function of various factors such as frequency reuse, carrier to
interface ratio, bit-energy to noise ratio, effective bit-rate per
connection and the like. As described in more detail below, the
bandwidth available to allocate to certain flows is geo-location
dependent, and time dependent based on current usage of other flows
in the geo-neighborhood.
The servers 14 are each connected to a mobile gateway 20 that
allocates bandwidth within the wireless network 10, routes traffic,
and tracts the location of the mobile devices 18 in the cells 12.
The position of a mobile device 18 may be determined using
network-assist, global position systems (GPS), and radio frequency
fingerprinting. Preferably, the positioning technique provides fast
and accurate information with respect to the location of the mobile
device 18 to minimize acquisition time for position information. As
mobile users move from cell 12 to cell 12, a handoff operation
between base stations 14 is performed by the mobile gateway 20.
The mobile gateway 20 provides connectivity from the wireless
portion of the network 10 to a wireline portion 24 of the network
10 via circuit switched and packet switch wireless data protocols.
The wireline portion 24 may be the Internet, intranet, extranet, or
other suitable local or wide area network. For the Internet, the
mobile gateway 20 provides an access, or entry point for all
transport control protocol/Internet protocol (TCP/IP) data
connections to the wireless portion of the network 10. The mobile
gateway 20 also provides connectivity from the wireless portion of
the network 10 to a wireline portion 25 of the network 10 via
circuit switched and packet switch wireless data protocols. The
wireline portion 25 may be a Public Switched Telephone Network
(PSTN), Integrated Services Digital Network (ISDN), broadband
integrated services digital network (B-ISDN), fiber distributed
data interface (FDDI), or other suitable local or wide area
network.
Each mobile gateway 20 may serve one or more servers 14, include
the RF front end and other functionality of a server 14, and/or may
be a wireless router as described in co-owned U.S. patent
application Ser. No. 09/513,914 titled Wireless Router and Method
for Processing Traffic in a Wireless Communications Network, filed
Feb. 25, 2000, and incorporated herein by reference. In the later
case, the wireless router may be self-configuring as described in
co-owned U.S. patent application Ser. No. 09/513,090, titled Method
and System for Configuring Wireless Routers and Networks, filed
Feb. 25, 2000, and incorporated herein by reference. Bandwidth
allocation and other functionality of the mobile gateways 20 may
instead be implemented by a mobile switching center (MSC), data
interworking function (IWF) devices, and other suitable network
devices without departing from the scope of the present
invention.
FIG. 2 illustrates details of the mobile gateway 20 for the
wireless network 10 in accordance with one embodiment of the
present invention. In this embodiment, the mobile gateway 20
comprises logic stored on computer-processable media. The logic may
comprise software stored on the computer-readable medium, or
hardware encoded in application specific integrated circuits
(ASIC), field programmable gate arrays (FPGA) and the like. The
software includes programs, modules, functions, database tables and
entries, data, routines, data storage, and other suitable elements
that may operate in the mobile gateway 20 or be distributed between
components of the wireless network 10. As described in more detail
below, the mobile gateway 20 combines geo-location information with
a dynamic bandwidth allocation and queue management mechanism to
deliver location-specific bandwidth efficiently and
cost-effectively.
Referring to FIG. 2, the mobile gateway 20 includes a data input
subsystem 32, a resource characterization subsystem 34 that uses
data from the input subsystem 32 to generate maps, profiles, and
other geo-location specific tools, a traffic control subsystem 36
that uses the tools and information generated by the resource
characterization subsystem 34 to implement allocation and
scheduling of wireless traffic in the wireless network 10 and
controls traffic between a network interface 38 and a wireless
interface 39. The data input, resource characterization, and
traffic control subsystems 32, 34, and 36 combine geo-location
information with a dynamic bandwidth allocation and queue
management mechanism to deliver location-specific bandwidth
efficiently and cost-effectively.
The data input subsystem 32 provides historical, empirical, field,
environmental, statistical, and other suitable data on or related
to the operation of the wireless network 10 or components within
the wireless network 10 that can be used to estimate bandwidth
demand, use, and interference within the wireless network 10. In
one embodiment, the data input subsystem 32 includes historical
data 40, QoS policies and service level agreement information 42,
allocation policy agreement information 44 and empirical, field,
and environmental data 46. The historical data 40 provides
historical performance data on the operation of the wireless
network 10. The historical data 40 is connection data gathered from
a switch, router, or other component external to and/or within the
wireless network 10. The historical data 40 may include for each
connection a time of day, call/service type, location, time until
move or change in location, and completion time.
The QoS policies and service level agreement information 42
provides information on service level agreements and QoS policies
of the business and consumers for the wireless network 10. The
allocation policy agreement information 44 provides allocations
policies and agreements for the wireless network 10. Provision of
the policies and agreement information 42 and 44 allows contractual
obligations to be accounted in allocated bandwidth within the
wireless network 10.
The empirical, field, and environmental data 46 provides
information that may be used along with historical data 40 to
allocate bandwidth within the wireless network 10. In one
embodiment, the empirical, field, and environmental data 46
includes empirical data per service type, location-specific RF
measurements, and location-specific interference estimates. The
empirical, field, and environmental data may be taken from
measurements within the wireless network 10, other suitable
components internal and/or external to the wireless network 10, or
treatises and statistical information available for wireless
networks.
The resource characterization subsystem 34 processes input data to
determine current and/or expected location-specific bandwidth
demand and/or use. In the illustrated embodiment, the resource
allocation subsystem 34 provides maps and profiles that are used to
determine allocation and/or scheduling of traffic in the wireless
network 10. The maps may be graphical maps, database entries
indexing the relevant information, and/or other suitable
representations of the data. In one embodiment, the resource
allocation subsystem 34 includes a source map 50, a subscriber
profile 52, a current usage map 54, a current demand map 56, an
expected demand map 58, and an interference contribution map 60. In
this embodiment, resource allocation subsystem 34 utilizes some or
all of the profiles and maps to allocate traffic on a per location
and per class basis.
The source map 50 characterizes bandwidth sources within a
geo-location area across time. The subscriber profiling 52 provides
a profile as to each subscriber's location, likelihood, or
probability of mobility and handoffs, likelihood of call hold time,
class of service and vocation, and the like. The current usage map
54 indicates the current usage and performance at specific
geo-location areas. The current demand map 56 indicates the
resource request at various geo-location areas at the current time.
The expected demand map 58 projects the expected resource request
for a specified time in the future. The expected demand map 58 may
be generated from the source map 50, subscriber profile 52, and the
current demand map 56. The interference contribution map 60
maintains data on the probability of interference contribution to
one or more servers 14 and the value of interference contribution
to the one or more servers 14.
The traffic control subsystem 36 allocates bandwidth on a per flow,
or per connection basis based on maps and profiles generated by the
resource characterization subsystem 34 and data generated by data
input subsystem 32, as well as other available data. Accordingly,
bandwidth is allocated on a per class and per location basis. The
traffic control subsystem 36 includes a soft handoff controller 48.
As described in more detail below, the soft handoff controller 48
directs and regulates servers 14 and determines primary service
status, soft handoff functionality, and power output for one or
more servers 14.
FIG. 3 illustrates a mobile unit in a soft handoff configuration in
accordance with one embodiment of the present invention. In this
embodiment, the soft handoff configuration 65 includes servers 71,
72, 73, 74, and 75. The servers 71-75 may be mobile base stations,
antennae, cell sites, cellular stations or other suitable servers
operable to communicate with a mobile unit 18. It will be
understood that the soft handoff configuration 65 may include any
number of additional servers, to cover additional surface area and
greater mobility within the wireless network 10.
Referring to FIG. 3, a mobile unit 18 is in soft handoff,
communicating with servers 71, 72, and 73 over wireless links 81,
82, and 83 at geo-location (1). The mobile unit 18 communicates
with the mobile switching center via all three of the servers 71,
72, and 73 while at position (1). Mobile unit 18 tracks the number
of servers 14 with which it is communicating through a list or
active set. In the illustrated example, the active set mobile unit
18 at geo-location (1) is {71, 72, 73}. Mobile unit 18 periodically
updates the active set by measuring the strength of the signals
from the neighboring servers 14.
The active set of mobile unit 18 is dependent on its geo-location
and the distance to neighboring servers, as well as signal strength
at a particular geo-location. For example, at geo-location (1),
mobile unit 18 will be unable to receive high quality transmissions
from server 74 because of the presence of obstruction 91 in the
path between mobile unit 18 and server 74. As described in more
detail below, resource allocation is controlled based on
characteristics of the wireless paths. In a particular embodiment,
a tiered active set is generated that minimizes the interference
and maintains the subscribed QoS for all users. In the illustrated
embodiment, the tiered active set prevents mobile unit 18 from
including server 74 in its active set, or reducing the power
allocation to zero. Thus, the resources of server 74 may be used
for other mobile units in the network 10.
As mentioned above, the geo-location of mobile unit 18 is important
in generating the active set. For example, as mobile unit 18 moves
from geo-location (1) to geo-location (2), the soft handoff
configuration will ensure that the active set is updated to reflect
the change in geo-location. In the illustrated example, the active
set of mobile unit 18 would change from {71, 72, 73} to {72, 73,
75}.
FIG. 4 illustrates a method for allocating wireless resources for a
soft handoff or other macro diversity connection in a wireless
network in accordance with one embodiment of the present invention.
In this embodiment, the connection is a CDMA, CDMA 2000, W-CDMA or
other suitable soft handoff between the mobile device 18 and cell
sites 12. The wireless resources are transmission resources
including transmission power and transmission bandwidth which are
proportional to one another.
Referring to FIG. 4, the method begins at step 200 in which a
request is received for cell site resources for mobile soft
handoff. In the CDMA embodiment, the request for cell site
resources includes an active set of cells 12 and a transmission
bandwidth for the cells 12. The active set and transmission
bandwidth are generated by the mobile device 18 upon initiating a
connection to the wireless network 10.
Proceeding to step 202, wireless path characteristics are
determined for each path between the mobile device 18 and the cell
12. The wireless paths are characterized based on their actual or
relative interference impact on the network 10 including the cell
12 in a region of the mobile device 18, neighboring cell 12, and/or
other mobile devices 18. The path characteristics comprise
historical data, QoS policies, service level agreements, empirical
data, field data, environmental data, and other data pertaining to
the operation of the wireless network 10 and collected by the data
input subsystem 32.
At step 204, cell 12 resources are individually allocated based on
the wireless path characteristics. For the CDMA embodiment,
transmission resources are allocated at each cell 12 based on
characteristics of the path between the cell 12 and the mobile
device 18. In this way, resource allocation is independently
controlled at each cell 12 to minimize interference for a soft
handoff connection while maintaining the connection at the
prescribed link quality. Thus, network managers can efficiently
manage air bandwidth and congestion in heavily loaded portions of
the network.
In a particular embodiment, as described in more detail below,
resources are allocated by dynamically creating a tiered active set
based on the active set generated by the mobile device 18. The
tiered active set is obtained from the active set by calculating
the biases for each cell 12 in the active set and restricting the
transmission resources allocated to each cell 12 from the mobile
user based on the biases.
FIG. 5 illustrates a method for determining soft handoff path
characteristics for resource allocation in accordance with one
embodiment of the present invention. Generally described,
characteristics are determined for each path by estimating the air
congestion in the cell 12, by using QoS subscriptions, or
treatments, of active users and/or applications, by estimating the
geo-location of the mobile device 18 and calculating average
regular frequency interference estimates based on historical,
real-time, and statistical system data, by estimating the
cross-pollution effect of neighboring cell 12, and/or by measuring
the mobile link performance parameters.
Referring to FIG. 5, the method begins at step 250 in which a
location-based characteristic is determined for the soft handoff
paths. The location-based characteristic is based on the geographic
location of the mobile device 18 relative to the cells 12 and
accounts for obstructions and other terrain undulations between the
mobile device 18 and the cells 12. This allows cells 12 with
negligible contributions to the overall link performance to be
identified and resources from the cells 12 to be retained by the
cells 12 for later allocation to connections.
Proceeding to step 252, a congestion-based characteristic is
determined for the wireless paths. The congestion-based
characteristic is based on the available bandwidth (power) at the
cells 12 to provide services to new users without violating the
subscriber constraints existing at the cell 12. The use of the
congestion-based characteristic reduces air congestion in the
network 10 and improves system capacity.
At step 254, a subscription-based characteristic is determined for
the wireless paths. The subscription-based characteristics include
grade of service (GoS) QoS, service level agreement constraints and
other suitable subscriptions properties. The subscription-based
characteristic allows resources to be allocated to provide link
performance proportional to the subscription. Thus, mobile
subscribers paying for higher quality link services will be
assigned greater resources while subscribers buying lower quality
will be assigned minimal resources.
At step 256, a performance-based characteristic is determined for
the wireless paths. The performance-based characteristic allows
redundancy in resource allocation to be identified and minimized
based on real-time performance parameters. Allocations based on
location, congestion and subscription characteristics can be
refined by the performance-based characteristic that is tied to
real-time performance parameters. In this way, resource allocation
is controlled to minimize interference between connections while
maintaining the subscribed requirements for all users. It will be
understood that the link characteristics may be determined from any
one of these characteristics or any combination of these
characteristics.
FIG. 6 is a flow diagram illustrating a method for allocating
resources for soft handoff connections using location-based
characteristics in accordance with one embodiment of the present
invention. The method begins at step 300 in which a requested set
of cells 12 and a requested bandwidth is received from the mobile
device 18. As previously described, the requested set of cells 12
comprises an active set identified by the mobile device 18 upon
initiation of a connection to the wireless network 10.
Proceeding to step 302, the geo-location of the mobile device 18 is
determined. The location of the mobile device 18 is determined
using GPS or any other suitable system. At step 304, path loss on
the paths between the mobile device 18 and each active cell 12 is
determined. The paths may be active or contemplated links. In one
embodiment, the path loss is the maximum allowable path loss
(MAPL). In this embodiment, the path loss is calculated using
Hata's model and terrain and building databases of the data input
subsystem 32 and using advanced radio frequency propagation (RF)
tools.
Next, at step 306, traffic loading of the network is determined in
the region of the mobile device 18. Traffic loading is determined
from the distribution of active users in the region and may be
obtained from historical, statistical network data collected over a
period of time by the data input subsystem 32. Using the location
of the mobile device 18 along with the path loss and traffic
loading, the minimum resources needed from each site in the active
set for the soft handoff connection can be determined.
At step 308, a bias is determined for each active cell 12 based on
the corresponding path loss, network loading and geo-location of
the mobile device 18. At step 310, the allocation bandwidth for
each active cell 12 is determined based on the corresponding bias.
In one embodiment, the allocation bandwidth is the requested
bandwidth multiplied by the bias. In this embodiment, the bias of
each cell 12 represents the fraction of the requested bandwidth
that will be allocated. It will be understood that allocation
bandwidth may be determined using location-based and other
characteristics independently of the requested bandwidth from the
mobile device.
Applying the bias values to the active set generates a tiered
active set of cell 12 for resource allocation. The tiered active
set includes the cells 12 of the active set with the bandwidth for
each site individually and/or independently adjusted based on the
location of the mobile device 18. Accordingly, the full requested
bandwidth may be allocated, none of the requested bandwidth may be
allocated, in which case the cell 12 does not communicate with the
mobile device 18, or a portion of the bandwidth may be allocated to
provide only the resources necessary to communicate with a device
18 given its current location.
At step 312, the allocation bandwidth is provided to the mobile
device 18 from the active cells 12. The provided allocation
bandwidth is the tiered active set including the cells 12 of the
active set with their bandwidth adjusted based on the location of
the mobile device 18. Step 312 leads to the end of the process by
which minimum resources needed from each cell 12 in an active set
to meet subscription requirements of the mobile user are determined
and allocated.
FIG. 7 illustrates a location-based soft handoff system in
accordance with one embodiment of the present invention. In this
embodiment, soft handoff configuration 350 includes servers 352,
354, and 356, which have 4, 3, and 2 units of bandwidth available,
respectively, for allocation to mobile users.
Referring to FIG. 7, mobile unit 18 is in soft handoff with servers
352, 254, and 356, and has an active set of {352, 354, 356}. The
mobile unit 18 requires a bandwidth of 2 units from each server in
its active set, which would exhaust the current available bandwidth
of server 356, leaving it unable to provide service to new
users.
As illustrated, the nearest server to mobile unit 18 is server 354.
However, because of the obstruction 360 in the signal path and
other terrain undulations, server 354 is not the optimal server for
mobile unit 18. Instead, server 352 is better situated to
communicate with mobile unit 18. Server 356 is located at a
relatively greater distance to mobile unit 18 than is server 352,
and therefore, server 356 is not the optimal server for mobile unit
18.
Using the empirical formula for path loss and the distribution of
the active users in the system, the biases for mobile unit 18 are
evaluated to be {1.0, 0.7, 0.0}. Therefore, the tiered active set
for mobile unit 18 is {1.0*2, 0.7*2, 0*2}, or {2, 1.4, 0}. That is,
mobile unit 18 is allocated 2 units of bandwidth from server 352,
1.4 units of bandwidth from server 354, and 0 units of bandwidth
from server 356. As server 356 is geo-located at a relatively large
distance from mobile unit 18, its contribution to the overall link
performance of the wireless link is negligible and is therefore
assigned a bias of 0.
Thus, servers 352, 354, and 356 still have 2, 1.6, and 1 units of
bandwidth, respectively, available for allocation to other mobile
units in their coverage areas. Without such controlled bandwidth
allocation, after allocation of resources in accordance with the
unbiased active set of mobile unit 18, {2, 2, 2}, only 2 and 1
units would remain available at servers 352 and 354 respectively.
Server 356 would have completely depleted its available bandwidth
and would have to deny access to new users.
FIG. 8 is a flow diagram illustrating a method for allocating
resources for soft handoff using a congestion-based characteristic
in accordance with one embodiment of the present invention. The
method begins at step 400 in which a request for a set of cells 12
and for a bandwidth is received from the mobile device 18. As
previously described, the requested cells 12 comprise an active set
identified by the mobile device 18 upon initiation of the
connection to the wireless network 10.
Proceeding to step 402, available bandwidth is determined at each
cell 12 in the active set. In one embodiment, the available
resources in each cell 12 is determined by measuring and/or
estimating the total and current transmit power, or bandwidth, at
each of the cells 12 and subtracting the current transmit power
from the total transmit power.
At step 404, a bias is determined for each cell 12 based on the
corresponding available bandwidth. In a particular embodiment, the
biases for the cells 12 are determined by calculating bandwidths
required for increasing larger cell sets to maintain the soft
handoff connection. Due to diversity gain, the required bandwidth
for the connection will decrease as the number of participating
cells increase. Thus, based on bandwidth availability, a single
site 12 may be able to maintain the link. If no single site has
sufficient available bandwidth, it is determined whether any two
cells 12 have sufficient bandwidth for a dual cell connection.
Similarly, if no two cells 12 have sufficient bandwidth, it is
determined whether any three sites have sufficient bandwidth for a
tri-cell connection, and so on, until either sufficient bandwidth
is determined to be available for the session at a set of the
active sites or sufficient bandwidth is unavailable, in which case
the connection is not accepted until bandwidth becomes available.
Upon determining a set of cells with sufficiently available
bandwidth, the bias for those cells is set to "1" for full
connectivity as requested by the mobile device 18 while the
remaining members of the active sets have a bias value set to
"0".
At step 406, the allocation bandwidth is determined for each cell
12 based on the corresponding bias. As previously described, the
allocation bandwidth may be the requested bandwidth multiplied by
the bias. For a bias value of "1", the allocation bandwidth will be
that requested by the mobile device. For a bias of "0", no
bandwidth from the cell 12 will be allocated. Applying the bias
values to the active set generates a tiered active set of cells 12
for resource allocation. The tiered active set includes the cells
12 of the active set with the bandwidth for each site individually
and/or independently adjusted based on real-time air
congestion.
At step 408, the allocation bandwidth is provided to the mobile
device 18 from the active cells 12. The provided allocation
bandwidth is the tiered active set including the cells 12 of the
active set with their bandwidth adjusted based on congestion in the
network 10. Step 408 leads to the end of the process by which the
number of cells 12 participating in the soft handoff connection are
minimized.
FIG. 9 illustrates a congestion-based soft handoff system in
accordance with one embodiment of the present invention. In this
embodiment, soft handoff configuration 450 includes servers 452,
454, and 456, which have 4, 3, and 1 units of bandwidth available,
respectively, for allocation to mobile users.
Referring to FIG. 9, mobile unit 18 is in soft handoff with servers
452, 454, and 456, and has an active set of {452, 454, 456}. The
mobile unit 18 requires a bandwidth of 1 unit from each server in
its active set, which would exhaust the current available bandwidth
of server 456, leaving it unable to provide service to new users,
such as mobile unit 18'.
As illustrated, at any instant, each server is transmitting power
to the active users in its coverage area, and to the users that are
in the soft handoff region of the server. By estimating the total
transmit power at each site, the bandwidth available at that server
can be estimated such that service may be provided to new users
without violating the grade of service and QoS constraints at the
server. Such estimates of the available bandwidth can be used to
generate the biases in the resource allocation.
Because available bandwidth is a function of total transmit power,
the greater the number of servers with which mobile unit 18 is
communicating, the less power is required by any particular server.
Thus, if the available bandwidth is such that mobile unit 18 can be
serviced by fewer servers, without unacceptable degradation of the
wireless link, the biases will be selected accordingly. In other
words, not all of the servers in the active set of mobile unit 18
will be allocated to communicating with mobile unit 18.
In the illustrated embodiment, the biases for mobile unit 18 are
set at {1, 1, 0}. Therefore, the tiered active set for mobile unit
18 becomes {1*1, 1*1, 0*1}. Accordingly, mobile unit 18 is
allocated 1 unit of bandwidth from server 452, 1 unit of bandwidth
from server 454, and 0 units of bandwidth from server 456.
Thus, servers 452, 454, and 456 still have 3, 2, and 1 units of
bandwidth, respectively, available for allocation to other mobile
units in their coverage areas. Without such controlled bandwidth
allocation, after allocation of resources in accordance with the
unbiased active set of mobile unit 18, {1, 1, 1}, server 456 would
have completely depleted its available bandwidth and would have to
deny access to new users. By selecting the biases in this manner,
server 456 preserves its 1 remaining unit of available bandwidth,
and may allocate it to mobile unit 18.
FIG. 10 is a flow diagram illustrating a method for allocating
resources for soft handoff using a subscription-based
characteristic in accordance with one embodiment of the present
invention. The method begins at step 500 in which a requested set
of cells 12 and a bandwidth is received from the mobile device 18.
The requested cells 12 comprise an active set that is identified by
the mobile device 18 upon initiation of the connection to the
wireless network 10.
Proceeding to step 502, a subscription-based characteristic is
determined for the mobile connection. The subscription-based
characteristic is a grade of service (GoS), QoS or other suitable
subscription type agreed to with the user. For the QoS embodiment,
the traffic may comprise high quality links for premium users,
intermediate quality links for assured users, and lower quality
links for best efforts users.
At step 504, a bias is determined for each cell 12 based on the
subscription-based characteristic. In one embodiment, a premium
subscriber is provided with all cells and bandwidths requested by
the mobile device 18. In this embodiment, a best-effort subscriber
is provided with only a single cell 12 for communication with the
network 10. Assured subscribers are provided with an intermediate
subset of the cells 12 requested by the mobile device 18. Thus,
bias of "1" will be assigned to all active cells 12 for a premium
subscriber and a bias of "1" will be assigned to a single cell 12
for a best-effort user with the remaining cells 12 having a bias of
"0". An assured subscriber will have a bias of "0" for one or more
of the active cells 12.
At step 506, the allocation bandwidth for each cell 12 is
determined based on the corresponding bias. As previously
discussed, the allocation bandwidth is requested bandwidth
multiplied by the bias. Accordingly, applying the bias value to the
active set of cells 12 generates a tiered active set of cells 12
for resource allocation. Cells 12 with a bias "1" will provide the
requested bandwidth while cell sites with a bias of "0" will
allocate no bandwidth to the mobile device 18.
At step 508, the allocation bandwidth is provided to the mobile
device 18 from the cells 12. The provided allocation bandwidth is a
tiered active set including the cells of the active set with the
bandwidth adjusted based on subscription types of the flows. Step
508 leads to the end of the process by which available resources
are fairly distributed amongst users according to their QoS
subscription and requirements.
FIG. 11 illustrates a subscription-based soft handoff system in
accordance with one embodiment of the present invention. In this
embodiment, soft handoff configuration 550 includes servers 552,
554, and 556, which have 2, 4, and 1 units of bandwidth available,
respectively, for allocation to mobile users.
Referring to FIG. 11, mobile units 560, 570, and 580 are each in
soft handoff with servers 552, 554, and 556, and each has an active
set of {552, 554, 556}. The mobile unit 560 requires a bandwidth of
1 unit from each server in its active set, which the illustrated
embodiment that allocation would exhaust the current available
bandwidth of server 556, leaving it unable to provide service to
the other mobile units 570 and 580. Furthermore, if the decision as
to which mobile unit receives the remaining available bandwidth of
server 556 is made on a first-come, first-serve basis, a
later-arriving mobile unit will be denied service. This results in
unfairness to any users who have subscribed to premium services,
but arrive on the network later than lower QoS subscribers. By
using a subscription-based soft handoff system, this problem is
reduced or eliminated.
As illustrated, users with different QoS subscriptions compete for
the same limited resources, the available bandwidth. The different
levels of QoS subscriptions are used to allocate resources. With
such selection criterion for the delivery mechanism, link
performance for the mobile user is proportional to its QoS
subscription. A mobile user subscribing to a higher QoS and
desiring a high quality link (i.e., premium users) will be assigned
a larger share of the available resources. Mobile users requiring
lower QoS (i.e., best effort users) will be assigned only minimal
resources.
In the illustrated embodiment, mobile user 560 is a premium
subscriber, mobile unit 570 is an assured subscriber, and mobile
unit 580 is a best effort subscriber. All three mobile units
require 1 unit of bandwidth. However, as server 556 has only 1 unit
of bandwidth available, depending on which mobile unit requests
first, server 556 may allocate the resource to mobile unit 580,
even though mobile unit 580 is only a best effort subscriber.
Furthermore, mobile units 560 and 570, who have subscribed to
higher levels of services will be allocated less resources.
By assigning biases based on the QoS subscription, mobile users are
allocated resources in accordance to their subscription class. For
example, premium users may be assigned bias values {1, 1, 1};
assured users may be assigned bias values {1, 1, 0}; and, best
effort users may be assigned bias values {1, 0, 0}. In the
illustrated embodiment, mobile unit 560 is assigned bias values {1,
1, 1}; mobile unit 570 is assigned bias values {1, 1, 0}; and,
mobile unit 580 is assigned bias values {0, 1, 0}. Accordingly,
mobile unit 560 will have a tiered active set of {1*1, 1*1, 1*1},
and will receive 1 unit of bandwidth from each server 552, 554, and
556. Mobile unit 570 will have a tiered active set of {1*1, 1*1,
0*1} and will receive 1 unit of bandwidth from servers 552 and 554,
and 0 units of bandwidth from server 556. Mobile unit 580 will have
a tiered active set of {0*1, 1*1, 0*1} and will receive 1 unit of
bandwidth from server 554 only, and 0 units of bandwidth from
servers 552 and 556.
Thus, mobile units 560, 570, and 580 each receive resources in
accordance with their QoS subscriptions. That is, mobile unit 560,
a premium user, receives a total of 3 units of bandwidth while
mobile user 580, a best effort user, receives only 1 unit of
bandwidth. Such an allocation will result in a fair distribution of
resources, wherein the user who has subscribed to a higher level of
service is provided with more resources than a user who has
subscribed to a lower level of service.
FIG. 12 is a flow diagram illustrating a method for allocating
resources for soft handoff connections using a performance-based
characteristic in accordance with one embodiment of the present
invention. The method begins at step 600 in which a request for a
set of cells 12 and a bandwidth level is received from the mobile
device 18. At step 602, a bias is determined for each cell 12 based
on path characteristics. The path characteristics may be
location-based characteristics, congestion-based characteristics,
and/or subscription-based characteristics.
Proceeding to step 604, the determined biases are compared to a
previous set of biases used to allocate bandwidth under which the
mobile device 18 is currently operating. Next, at decisional step
606, the mobile device 18 determines whether the biases have
changed form the previous set. If the biases have not changed, the
No branch of decisional step 606 leads to step 608 in which the
adequacy of current resource allocation is determined. In one
embodiment, the adequacy is determined based on whatever an
acknowledgement was received and, if no acknowledgement was
received, whether a timer has expired in which case insufficient
resources were allocated. The acknowledgement may be based on
packet error rates, round trip delays and packet
retransmissions.
Proceeding to decisional step 610, if sufficient resources are not
allocated, the No branch of decisional step 610 returns to step 602
in which the biases are recomputed in order to improve link quality
if sufficient resources have been allocated, the Yes branch of
decisional step 610 leads to step 612. The Yes branch of decisional
step 606 also leads to step 612 in which allocation for each
requested cell 12 is determined by applying on the corresponding
biases to generate the tiered active set. At step 614, the
allocated bandwidth is provided to the mobile device 18 from the
cell 12. Step 614 leads it into the process by which resource
allocation is refined dynamically based on real-time performance
parameters to minimize the redundancy of resource allocation while
maintaining required link quality.
FIG. 13 illustrates a performance-based soft handoff system in
accordance with one embodiment of the present invention. In this
embodiment, soft handoff configuration 650 includes servers 652,
654, and 656, which each have 2 units of bandwidth available for
allocation to mobile users.
Referring to FIG. 13, mobile unit 18 is in soft handoff with
servers 652, 654, and 656, and has an active set of {652, 654,
656}. The mobile unit 18 requires a bandwidth of 1 unit from each
server in its active set. By analyzing certain performance
parameters collected in real time, unnecessary redundancy in the
resource allocation can be estimated and minimized by calculating
appropriate biases. This technique is similar to that based on
geo-location of the mobile unit, discussed in conjunction with
FIGS. 6 and 7 above, except that real time performance parameters
are used to estimate the biases. The biases are recalculated at
regular intervals and adjusted according to the measured
performance of the link. The performance parameters include packet
error rates, round trip delays, and packet retransmissions.
In the illustrated embodiment, mobile unit 18 begins with a first
set of bias values {1, 1, 1}. It will be understood that the
initial bias values may be calculated using any one of the
above-mentioned methods, or a combination of the above-mentioned
methods. For the duration of the wireless link connection,
performance data is collected, consisting of packet error rates,
round trip delays, and packet retransmissions. At the next bias
recalculation interval, the collected data is used to evaluate the
quality of the link.
If the quality of the link is well above acceptable levels,
unnecessary redundant resources unallocated to mobile unit 18 by an
adjustment in the bias values. The bias adjustment may have the
effect of removing servers from communication with mobile unit 18
entirely, partially reducing the bandwidth allocated by a
particular server to mobile unit 18, or a combination of the two
effects. In the illustrated embodiment, one server, server 656, is
removed from communication with mobile unit 18. This is effected by
adjusting the bias values for mobile unit 18 to {1, 1, 0}. Thus,
the second tiered active set for mobile unit 18 becomes {1*1, 1*1,
0*1}, and mobile unit 18 receives 1 unit of bandwidth from servers
652 and 654, and 0 units of bandwidth from server 656. Performance
data is continually collected and at the next bias recalculation
interval, the collected data is again used to evaluate the quality
of the link.
If the quality of the link has degraded to below acceptable levels,
additional resources are allocated to mobile unit 18 to restore
acceptable service. Adding resources is effected by an upward
adjustment in the bias values, which may have the effect of adding
servers to communication with mobile unit 18, increasing the
bandwidth allocated by servers already in communication with mobile
unit 18, or a combination of the two effects. In the illustrated
embodiment, bandwidth from a server already in communication with
mobile unit 18 is increased. This is accomplished by adjusting the
bias values of mobile unit 18 to {1, 1.5, 0}, and the third tiered
active set for mobile unit 18 becomes {1*1, 1.5*1, 0*1}. Thus,
mobile unit 18 receives 1 unit of bandwidth from server 652, 1.5
units of bandwidth from server 654, and 0 units of bandwidth from
server 656.
As illustrated, the repeated bias modifications ensure that
resource allocation is adequate to maintain link quality while
minimizing unnecessary redundant resources which may then be
allocated to other mobile users.
Although the present invention has been described with several
embodiments, various changes and modifications may be suggested to
one skilled in the art. It is intended that the present invention
encompass such changes and modifications as fall within the scope
of the appended claims.
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